Mg/Ca

[lcs]

I'm getting ready to do a 10% water change this morning so I decided to test Mg and Ca before I started and, boy, was I surprised at the readings . . .

Mg - undetectable
Ca - 600ppm

What the heck is going on? I'm using Seachem Reef salt and I do 5-10% every week or two. Why is it so wacky?? Could this explain why I can't keep zoas happy?

I'm planning on testing after the water change as well. I'm considering changing my salt, that's for sure.

 

[Gary Majchrzak]

in most cases

in most cases

water changes ALONE cannot keep up with the demands of growing reef organisms. This is why people choose and implement a calcium, alkalinity and magnesium replacement scheme IN ADDITION TO regular partial water changes

 

[Gary Majchrzak]

are you sure that your test kits are accurate and reliable?

 

[lcs]

About an hour after the water change:

Ca - 500
Mg - <100
Alk - high end of normal with Red Sea kit

are you sure that your test kits are accurate and reliable?

I think so. They're not that old and they seemed to be fine the last time I used them a couple months ago. The Mg is Salifert and the Ca in RedSea.

water changes ALONE cannot keep up with the demands of growing reef organisms.

I'm getting a better appreciation for this lately. I had been under the impression that a tank lightly stocked (or in my case very lightly) with corals would not have a large impact on these elements given frequent water changes. I will be adding supplementation as soon as I can, that's for sure!

 

[Gravesj1s]

-lcs,

Just some thoughts here,after rereading your other thread about Mg supplement.

You mentioned your tank is only 3 months old and you just added 50lbs of live rock.This could be why you were seeing "cloudy water".-(bacterial bloom)
Honestly, you might want to test for ammonia. I would not bother testing anything other than the following.
Ammonia,nitrite,alk,temp,specif gravity.

 

[Conesus_Kid]

What units are you using to measure Mg? I have a tough time understanding how you could have less than 100 ppm Mg right after a water change.

Are you using a calibrated refractometer to measure salinity?

 

[sg1838]

I too have to question your test kits, or your testing methods. I'm not sure what sea salt you are using, but I typically use Reef Crystals. Without supplementing at all, my Mg was at 1200 ppm. I can't say what my Ca would be at if I didn't supplement at all, but I'm guessing that it wouldn't be below 300 ppm, and I KNOW it wouldn't be above 450 ppm.

But, I'm not an expert aquarist chemist - maybe you can get crazy values if your tank isn't fully cycled, or something else is completely out of whack.

Personally, I'd be looking to purchase / borrow some more test kits (I just replaced a few of mine that were quite old).

Good luck!

 

[lcs]

You mentioned your tank is only 3 months old and you just added 50lbs of live rock.

The tank has been cycled since early September and the 40lb of dead rock was added at the end of July.

I have a tough time understanding how you could have less than 100 ppm Mg right after a water change.

I know! I don't get it either. It's a Salifert test kit that is only about six months old and worked just fine when I last used it a couple of months ago. Fine as in a reading of about 1400ppm.

Are you using a calibrated refractometer to measure salinity?

Unfortunately, no.

I think I will retest again tomorrow and see what I get. If things still seem wacky I'll stop over to MO and have them run them for me and see what happens.

I will also test newly made water and see what that shows.